Speed indicating means sensitive to water pressure, which varies in accordance with the speed of the watercraft, have long been employed. The indicating means generally comprises a gauge, having units in knots or miles per hour, mounted on the watercraft at a position which is visible by the operator of the craft. The gauge is adapted to be actuated by the water pressure sensed by a pitot tube positioned in the water and having an orifice opening facing the direction of travel of the watercraft.
Sometimes the pitot tube for indicating the speed is mounted to the watercraft and extends beneath the hull. However, such an installation is generally inoperative and/or erratic when mounted on a hydroplaning boat which is frequently airborne for brief periods of time when travelling at high speeds. In addition, the pressure tube may also be incorporated integrally into the propulsion structure as can be seen in U.S. Pat. No. 2,627,181. However, with the orifice disposed above the gear case, as shown in that patent, the pressure tube is generally inoperative at high speeds as the gear case may be almost wholly out of the water with only lower end carrying the propeller engaging the water.
A second prior art reference, U.S. Pat. No. 3,210,995, teaches an arrangement in which the pitot tube is provided in the lower housing and comprises a generally horizontal fore-and-aft extending tubular passage disposed in the skeg adjacent to and spaced from the lower extremity of the motor. The tubular passage extends rearwardly from the leading edge of the skeg and provides an opening facing the forward direction of travel of the watercraft. Although this arrangement insures that the pressure tube is always in fluid communication with the water being traversed by the watercraft, the costs, labor and machining difficulties associated with manufacturing a tubular passage within the skeg of the motor make this arrangement a fairly expensive solution to the problem at hand. In addition, as the orifice opening is toward the rearward portion of the propulsion device, it can be influenced by the wake and other interference caused by the forward most portion of the propulsion device and this somewhat effects the accuracy and reliability of the sensed pressure.
The basic purpose of a nose cone is to streamline the gear case so as to increase the top speed and improve the handling of the watercraft. The nose cone may or may not be provided with cooling water inlet ports, located on the lower most portion of the casing, associated with an internal ducting in the nose cone and a water outlet provided above the water line. When present, this ensures that a steady source of cooling water is provided to the engine even when the engine is raised on the watercraft's transom to further increase the top speed and performance.
Wherefore, it is generally an object of the invention to provide a water pressure sensing arrangement which will sense the true instantaneous pressure and thereby accurately indicate the speed of the watercraft regardless of the position of the motor relative to the water surface.
It is a further object of the invention to provide a nose cone which is easily adaptable to the forward portion of outboard and outboard/inboard motors alike.
A still further object of the invention is to provide a water pressure sensor which can be easily cast or molded into a nose cone of a propulsion device and thereby reduce the cost and labor associated with machining a bore through various portions of a motor.